Assessment and prediction of coastal saline soil improvement effects combining substrate amendments and salt barrier materials in typical region of the Yangtze River Delta

Coastal saline regions are characterized by high salinity, low permeability, organic matter deficiency, shallow groundwater depth, which limit leaching and lead to salt return. However, there remains a lack of targeted research on long-term coastal saline soil improvement by combining permeation promotion and salt return suppression. Based on a case study of the coastal saline area of Jiangsu Province, China, we used dynamic monitoring of soil water and salt transport, along with laboratory and field scale experiments to analyze the effect of combining substrate amendments and salt barrier materials on salt leaching and return. And numerical simulations were used to predicted the effects of the optimized combination improvement schemes under different climatic conditions in the future. The 2–4% (w/w) straw amended soil had a greater increase (＞90%) in desalinization ratio and a higher reduction (more than half) in desalination time due to changes in soil physical properties. The geocomposite isolated salt effectively due to the formation of capillary barrier compared with traditional straw burial. The results of field scale experiments and numerical simulations showed that geocomposite salt barrier material combined with straw substrate amendment scheme provides a cost-effective solution of soil salinization in coastal areas. • Organic amendments plus salt barrier materials increased soil desalination rate by 90%. • HYDRUS-2D modelling predicted ten-year outcomes of alternatives for managing saline soil. • Laboratory and field experiments supported the modelling. • Soil improvements were maintained over ten years. • Numerical simulation methods offered a scientific basis for managing saline soil.